A fuel cell, particularly a solid polymer fuel cell is greatly expected as a next-generation power generating system and has advantages that the operating temperature is lower and the fuel cell is compact as compared to fuel cells of other types, and it is expected as a promising power source for home use and automobiles for these advantages. A solid polymer fuel cell has a layered structure consisting of a hydrogen electrode, an air electrode and a solid polymer electrolyte membrane sandwiched between these electrodes. Incidentally, a hydrogen-containing fuel is supplied to a hydrogen electrode and oxygen or air is supplied to an air electrode, respectively, and electric power is drawn out by oxidation and reduction reactions that occur in each electrode. Moreover, a mixture of a catalyst for promoting the electrochemical reaction and the solid electrolyte is generally applied to both electrodes.
As the catalyst constituting the electrodes described above, a precious metal, in particular a platinum catalyst supporting platinum is widely used as a catalyst metal hitherto. This is because platinum as a catalyst metal exhibits high activity upon promoting the electrode reaction in both the fuel electrode and the hydrogen electrode.
Meanwhile, in recent years, the investigation cases on an alloy catalyst to apply an alloy of platinum and another metal as a catalyst metal have increased in order to secure the catalytic activity while decreasing the amount of platinum used for the cost reduction of a catalyst. Particularly, a Pt—Co catalyst adopting an alloy of platinum and cobalt as catalyst particles is known as a catalyst that can exert higher activity than that of the platinum catalyst even though the amount of platinum used is decreased (Patent Document 1). Moreover, a ternary alloy catalyst (Pt—Co-M alloy) in which a third metal element (M) is alloyed in order to further improve the Pt—Co catalyst has also been reported (Patent Document 2).